HEAT RECOVERY APPARATUS FOR AIR HEATING AND EXCHANGING SYSTEM

Abstract: A heat recovery unit (1) for an air heat exchange system comprises a box-like unit shell (12), a counter-flow type heat exchanger (2), a first fan (3) for distributing outdoor air and supply air and a second fan (4) for distributing exhaust air and extract air, insulation elements (21-29) for sound reduction and thermal insulation, an internally insulated front door, and ducts (7-11) for outdoor air, supply air, exhaust air, and extract air. The heat exchanger (2), having a width corresponding to the depth of said unit sheel (12), is disposed so as to be sealingly in close contact with the rear wall (13) and front door, respectively, of said unit shell (12) and to be sealingly in close contact with the short sides (16, 17) of said unit shell (12). Thereby, said unit (1) is divided into two separate spaces, a supply air space (B) and an exhaust air space (A), said first fan (3) being mounted in said supply air space (B) and said second fan (4) being mounted in said exhaust air space (A). Said fans (3, 4) and said ducts (7-11) are surrounded by said thermally insulating and sound reducing insulation elements (21-29).

Description: Heat recovery apparatus for air heating and exchanging system. This invention relates to heat recovery units for air heat exchange systems, and specifically to a heat recovery unit intended for installation in dwelling spaces. It has been known for a long time, that heat recovery units intended for installation in dwelling spaces present problems in keeping the sound level at a reasonable level in the room, where it is mounted. The highest sound level permitted of 35 dBA will usually be exceeded. The sound of the fans of the heat recovery unit escapes in part directly from the unit itself and partly over the supply air and exhaust air ducts. The reason for this sound problem is primarily to be found in the lack of sound reducing insulation material within the unit, in which -the unit is located. The fundamental reason for this is that there is a lack of space for insulation within the unit, this in turn resulting from the bulkiness or inappropriate location of, above all, the heat-exchanger in the heat recovery unit and by the external dimensions of the heat recovery unit being predetermined through current standard regulations. The location of the fans within the unit may also contribute to this sound problem. Heat recovery units of the kind in question are intended to be installed in a kitchen above the stove hood, usually covered by a spice rack, or in a scullery, a laundry-room or the like. Should the heat recovery unit be placed in such a space, the space available therefor will be limited, this in turn limiting the space available to fans, sound insulation and other necessary equipment. In conventional heat recovery units, a cross-flow type heat- exchanger (see, e.g., ABB F AKT, RDK or ACF type) is generally used. Cross-flow type heat-exchangers are bulky and will thus occupy a major part of the space available and will thus impose restrictions to the possibilities for fan location, thereby reducing the space available to sound insulation. This makes it difficult to attain a sound level below the stipulated 35 dBA level in the kitchen with this type and a standardized basic ventilation. It is also well-known to use counter flow heat-exchangers in heat recovery units (see, e.g., Essvex, marketed by Enessen AB, Skanninge, Sweden, or Temovex of Astorp, Sweden). Since it is difficult to place this heat-exchanger in the heat recovery unit in a satisfactory manner, the possibility to place the fans has nevertheless been limited, and, as a result, the space available for sound insulation has been reduced, this leading to the above- stated problem. Hitherto, the importance of the placing of the fans within the unit has probably been underestimated, letting their location as well as the flow path result from the placing of the heat- exchanger. Also, the thickness of the sound insulation is of major importan¬ ce in order to have the highly disturbing low-frequency sound attenuate . The object of this invention is to solve the above-stated problem, namely to reduce the sound level of a heat recovery unit in a unit room by at least 3 - 4 dBA in comparison to convention¬ al units, while maintaining a high efficiency and at a low cost. This object is achieved through a unit of the type stated in the patent claims, which claims also disclose the particular features of the invention. The invention will now be described with reference to the appended drawings, wherein: FIG. 1 shows a schematic view of a heat recovery unit of this invention, FIG. 2 shows an enlarged first space of said unit of fig. 1, FIG. 3 shows outdoor air, supply air, exhaust air and extract air ducts of the heat recovery unit of the heat recovery unit of this invention, and FIG. 4 shows in two schematic views, 4a and 4b, respec¬ tively, the way in which an extract air duct extends from a fan. The heat recovery unit of fig. 1 basically comprises a counter- flow type heat-exchanger 2, two fans 3 and 4 for distributing air, and insulation elements for sound reduction and thermal insulation. A guide plate 5 and 6 is disposed on the fans 3 and 4, respectively, for guiding the air stream so as to prevent undue turbulence. The heat recovery unit 1 further comprises a first exhaust air duct 7, a second exhaust air duct 8, an extract air duct 9, an outdoor air duct 10 and a supply air duct 11, which extend through the unit, as well as, not shown, convention¬ al filters and an electrical after-heater to regulate the temperature of the supply air. The entire heat recovery unit is defined by a box-like unit shell 12 having an also conventionally openable front door (not shown). The shell 12 is provided with a rear wall 13 opposite the open front side, two long sides 14, 15 and two short sides 16, 17, the exhaust air duct 7 extending through the one short side 16, while the other ducts 8 - 11 extends . through the opposing short side 17, which is intended to be facing upwards with the unit 1 in its mounted position. The heat-exchanger 2, which has the shape of a rectangular, relatively flat box, is disposed to be extended through the unit 1 between the two opposing short walls 16, 17, having one of its two long sides resting against the rear wall 13, and its other long side resting against the front door, the heat-exchanger 2 dividing the unit 1 into two sections A and B, which are sealed with respect to one another. The side of the front door facing inwards towards the unit is insulated for sound reduction and for thermal insulation by means of mineral wool or an equivalent material. The first space A, shown in fig. 2, houses the fan 4 and its associated guide plate 6, insulation elements 21 - 24 and the ducts 7, 8, 9, and filters. The fan 4, belonging to the radial type, is disposed in the central area of the first space A. With this location, the sound from the fan may be largely limited by the extensive insulation, which surrounds the fan 4. The highly advantageous shape of the duct 9 at the transition from the rectangular duct shape of the fan outlet to the circular shape of the outlet (see fig. 4) also contributes to a low sound level. • The insulation elements 21 - 24, mainly consisting of mineral wool or an equivalent material and being surrounded to a greater or lesser extent by sheet metal frames in order to be kept together and to be attachable in position within the heat recovery unit 1, are disc- and wedge-shaped and all have a width, which corresponds to the depth of the unit 1, i.e. the distance between the rear wall 12 and the front door of the unit shell 12. Thereby, the insulation element 21 preferably has a thickness of 40 - 60 mm, the insulation element 2230 - 130 mm, the insulation element 23 appr. 30 mm, and the insulation element 24 appr. 140 mm. The insulation element 21 is disposed in front of the axial intake opening of the fan 4, having one of its two sides sealingly resting against the central area of the hea -exchanger 2 and its free end directed towards one 17 of the two short sides of the unit shell 12. The area between the fan 4 and the insulation element, in which further the guide plate 6 is housed, constitutes a part of the extract air duct, which at that location then is a duct, into which both ducts 7 and 8 have merged. The insulation element 22 is disposed between the fan 4 and adjacent short side 16 of the unit shell 12 and extends substan¬ tially perpendicularly to the heat-exchanger 2 to lie close to the heat-exchanger as well as to the insulation elements 21 and 23. Said combined exhaust air duct 7, 8 having here a cross- sectional area, which increases towards the heat-exchanger 2, continues between the insulation element 22 and the opposing short side of the unit shell 12. The insulation element 23 is disposed between the fan 4 and the adjacent long side 15 of the unit shell 12 and in parallel thereto. The insulation element 23 is disposed at a distance from the adjacent long side 15 of the unit shell, 12, thereby creating an exhaust air duct 8 from the exhaust air inlet in the short wall 17 to the combined exhaust air duct 7, 8. The one short end of the insulation element 23 rests against the insulation element 22 and the other short end thereof rests against the insulation element 22 and the other short end thereof rests against the insulation element 24, which houses the duct 9 leading from the fan 4. The insulation element 24 is disposed between the short side 17 of the unit shell 12 and, respectively, fan 4 and insulation element 23. The insulation element 24 extends between the rear wall 13 of the unit shell 12 and the front door thereof, has a considerable thickness and encloses the duct 9 leading from the fan 4. .The insulation elements 21, 22, 23, 24 thus form a substantially C-shaped enclosure of about 340° around the fan 4. The second space B comprises the fan 3 and a guide plate 5 associated therewith, insulation elements 25, 26, 27, 28, 29, an electrical after-heater 30, an outdoor air duct 10 and a supply air duct 11, and a filter (not shown). The fan 3 is located in the corner of unit 1 formed by the long side 14 and the short side 16. An effective insulation element 25 is inserted between the fan 3 and the short side 16. A further insulation element 26 is placed at the central area of the heat- exchanger 2, to which it lies close. From the end of insulation element 26 facing the short side 17, the insulation element 27 extends outwardly to this short side 17. A thick insulation element 28 is provided between the fan 3 and the long side 14. The insulation elements 25, 26, 28 encloses the fan 3 over about 320°. The supply air duct 11 extends from the fan 3 to the outside through the short side 17. The duct 11 is lined internal¬ ly with an effective acoustical and thermal insulation 29. The electrical after-heater 30 is disposed in the duct 11 to heat the supply air from the fan 3. Figure 3 schematically illustrates the way the outdoor air, supply air, exhaust air and extract air ducts extend through the unit 1. The exhaust air from, e.g., a bathroom, a laundry-room and a stove hood will be sucked into the ducts 7 and 8 by the fan 4 and will then pass through the heat-exchanger 2 and expelled through the extract air duct 9. This is a part of the function of the unit, which takes place in the space A, which space is separated from the second space B of the unit by the heat- exchanger 2. The outdoor air duct 10 extends in the space B, the outdoor air being sucked in through the heat-exchanger 2 to the fan 3 and expelled therefrom into the dwelling space, or the like, through the supply air duct 11. At this time, the supply air will also pass through the heater 30, which will impose a set minimum temperature on the supply air. This is a part of the function of the unit taking place in the space B. Figure 3 also shows the way in which large amounts of acoustically and thermally insulating material, through this invention, can be fit around the fans 3, 4 as well as around the ducts 7 - 11 in the unit, while at the same time offering an easy access to all details for servicing purposes. Here, it should be noted that the two air systems in the spaces A and B, respectively, are separated in an insulating manner to a degree, such that no mixing of the air streams will be possible. Fig. 4a and 4b demonstrates the way in which the duct 9 not only abandons a rectangular shape at the outlet of the fan 4, but also extends with an increasing cross-sectional area from the fan 4 while deviating in two distinct directions, one extending across the fan and one towards a side of the fan. This shape has proved to be optimal for achieving a maximum efficiency of the fan 4 and a minimum sound level. Through the present invention, the object set-forth in the beginning has been achieved, namely to provide a conventional size ventilation and heat recovery unit having a high efficiency and operating, under normal operating conditions, well below a sound level indicated as the highest permitted sound level within the space, in which the unit is mounted. Of course, various embodiments of the invention are possible, although only one preferred embodiment thereof is disclosed. Such different embodiments are, however, intended to lie within the scope of the appended claims.

Claims: PATENT CLAIMS 1. A heat recovery unit (1) for an air heat exchange system comprising a box-like unit shell (12), a counter-flow type heat- exchanger (2), a first fan (3) for distributing outdoor air and supply air and a second fan (4) for distributing exhaust air and extract air, insulation elements (21 - 29) for sound reduction and thermal insulation, an internally insulated front door, and ducts (7 - 11) for outdoor air, supply air, exhaust air, and extract air, characterized in that said heat-exchanger (2), having a width corresponding to the depth of said unit shell (12), is disposed so as to lie sealingly close to the rear wall (13) and front door, respectively, of said unit shell (12) and to lie sealingly close to the short sides (16,17) of said unit shell (12), thus dividing said unit (1) into two separate spaces, a supply air space (B) and an exhaust air space (A), said first fan (3) being mounted in said supply air space (B) and said second fan (4) being mounted in said exhaust air space (A), and that said fans (3,4) and said ducts (7 - 11) are surrounded by said thermally insulating and sound reducing insulation elements (21 - 29). 2. The heat recovery unit (1 ) according to claim 1, character¬ ized in that said second fan (4) is located centrally in said exhaust air space (A), thereby being surrounded of a C-shaped insulation (21 - 24). 3. The heat recovery unit (1) according to claim 1 or claim 2, characterized in that the sound generated by said second fan (4) in said exhaust air space (A) is made to pass at least some of said insulation elements (21 - 24), which surround said second fan (4) in a C-shape, as well as said heat-exchanger (2) before reaching said exhaust air ducts (7,8), during which passage the sound level is reduced. 4. The heat recovery unit (1) according to anyone of the preceding claims, characterized in that said exhaust air duct (9) leading from said second fan (4) presents a cross-sectional shape which, when viewed in the flow direction, changes from rectangu¬ lar to circular and deviates into two optimum directions for said fan (4). 5. The heat recovery unit (1 ) according to anyone of the preceding claims, characterized in that at least some of said insulation elements (21 - 29) present a width corresponding to the depth of said unit shell (12), that a first insulation element (21) is disposed in front of the inlet of said fan (4) and lies tightly close to the central area of said heat-exchanger (2), that a second insulation element (22) is extended between the one short side (16) of said unit (1) and said second fan (3) from said first insulation element (21) and towards the adjacent first long side (15) of said unit (1), that a third insulation element (23) is extended from said second insulation element (22) past said second fan (24) and in parallel with said first long side (15) of said unit (1), and in that a fourth insulation element (24) is disposed between said second fan (4) and said one short side (17) of said unit (17) and in connection with said third insulation element (23) . 6. The heat recovery unit (1) according to anyone of the preceding claims, characterized in that said first insulation element (21 ) , being slightly wedge-shaped and having a flattened tip, presents a thickness of 40 - 60 mm, that said second insulation element (22), being strongly wedge-shaped and having a flattened tip, presents a thickness of 30 - 130 mm, that said third insulation element (23), being disc-shaped, presents a thickness of 30 mm, and that said fourth insulation element (24) presents a thickness of approximately 140 mm and houses said extract air duct (9 ) from said second fan (4) . 7. The heat recovery unit (1 ) according to anyone of the preceding claims, characterized by said first fan (3) being surrounded, preferably over 320°, by sound reducing insulation elements (25, 26, 28), and said first fan as well as an electron¬ ical after-heater (30) being arranged in said second space (B) . 8. The heat recovery unit (1) according to anyone of the preceding claims, characterized by said supply air duct (11) from said first fan (3) being completely sound-insulated and having a length exceeding half the height of said unit (1). 9. The heat recovery unit (1) according to anyone of the preceding claims, characterized by said insulation elements (21 - 29) consisting of mineral wool. 10. The heat recovery unit (1) according to anyone of the preceding claims, characterized by one or more of said insula¬ tion elements (21 -29) at least partly being enclosed by sheet metal pieces and/or sheet metal frames.

Inventors: OESTBERG HANS, OESTBERG, HANS
Applicants: OESTBERG HANS, OESTBERG, HANS
Application year: 1994
Main classification: F24F12
IPC codes: F24F12, F24F13